1. Field of the Invention
The present invention relates to a focus retaining mechanism, and more particularly, to a focus retaining mechanism of a camera.
2. Description of the Prior Art
Please refer to FIG. 1 of a top view of a conventional lens driving device 10 of a camera. The lens driving device 10 is disclosed in U.S. Pat. No. 5,680,649 xe2x80x9cLENS DRIVING DEVICE FOR AUTO-FOCUS CAMERAxe2x80x9d. The lens driving device 10 comprises a base 12 comprising a cylindrical opening16, a focusing lens 14 rotatably mounted within the opening16, a lens setting ring 40 rotatably mounted on the periphery of the opening 16 on the base 12, a driving ring 44 mounted on the base 12 by hooking the lens setting ring 40, a cam portion 42, a lens barrel 18 mounted on the base 12 by hooking the lens setting ring 40 and the cam portion 42, a first bi-directional driving motor 20 and a second bidirectional driving motor 30 mounted on the base 12, a spring 34 mounted on the base 12, and a retainer member 22 disposed on the base 12. In addition, a cylindrical projection 46 disposed on the lens setting ring 40 hooks an engaging portion 19 of the lens barrel 18. Thus, when the lens setting ring 40 is rotated, the lens barrel 18 and the focusing lens 14 are also rotated. The second bidirectional driving motor 30 is used to rotate the driving ring 44 for controlling a shutter. The first bi-directional driving motor 20 is used to drive the retainer member 22 for mounting the cam portion 42 in a predetermined position so as to rotate the focusing lens 14 to a corresponded position. Moreover, an idler gear 70 and a first ratchet 50 are used for the transmission between the cam portion 42 and the retainer member 22.
As shown in FIG. 1, when the second bi-directional driving motor rotates the driving ring 44 toward a positive direction via a second ratchet 32 to control an opening position of the shutter, the driving ring 44 moves the lens setting ring 40 so as to rotate the lens barrel 18 and focusing lens 14. At the same time, the lens setting ring 40 also moves the retaining member 22 so that a plurality of gear portions 43 hook with a hold lever 60 one by one. The retaining member 22 rotates the first ratchet 50 by hooking the idler gear 70.
When the second bi-directional driving motor 30 moves the driving ring 44 toward a positive direction to a predetermined position, which is an appropriate position for focusing, the first bi-directional driving motor 20 controls the retainer member 22 to stop rotating the first ratchet 50. At this time, a pull-back action to the retaining member 22 generated by the flexible component 34 is stopped due to the stop action of the retainer member 22. Thus, the lens barrel 19 and the driving ring 44 do not circumrotate so that the lens driving device 10 can focus and retain position. At this time, the driving ring 44 moves to a predetermined shutter position and opens the shutter, and the lens barrel 18 also drives the focusing lens 14 to rotate to a corresponding position.
The second bi-directional driving motor 30 continues to rotate in a positive direction and moves the driving ring 44 to an utmost position 45. At the same time, the first bi-directional driving motor 20 drives the retainer member 22 to rotate the first ratchet 50 so that the first ratchet 50 and the cam portion 42 rotate to corresponding utmost positions. At this time, the second bi-directional driving motor 30 provides no power to the lens driving device 10. That means after the second bi-directional driving motor 30 moves the driving ring 44 to a utmost position 45, only the first bi-directional driving motor 20 provides a small amount of power to back focus retaining structures such as the first ratchet 50, the cam portion 42, the lens barrel 18, the driving ring 44, and the flexible component 14 to an initial state. After the first bi-directional driving motor 20 drives the retainer member 22 and the first ratchet 50 to their utmost positions, the first ratchet 50 does not contact with the retainer member 22, and a spring 62 disposed on the base 12 pulls the hold lever 60 back to the initial state. This is an action of closing the shutter. In addition, the flexible component 34 also pulls the cam portion 42 back to the initial state so that the driving ring 44, lens barrel 18, and the first ratchet 50 are also moved back to the initial states.
As described above, the conventional lens driving device 10 has a complicated focus retaining structure, and a retainer member and a gear assembly are needed. Thus, the complexity and costs of components are increased. This highly complicated structure hardly reduces costs of assembly. In addition, although the retainer member 22 acts effectively, the available space of the lens driving device 10 is decreased with the use of the retainer member 22.
It is therefore a primary objective of the claimed invention to provide a focus retaining mechanism to solve the above-mentioned problems.
The claimed invention provides a focus retaining mechanism of a camera. The camera comprises a base, a focusing lens, a retaining member, and a retaining hook. The base comprises a cylindrical and vertical opening therein. The focusing lens is rotationally fixed within the opening. The retaining member is horizontally and movably fixed in the base. The horizontal sides of the retaining member include a ratchet side, a smooth side, a first end and a second end positioned over the connecting portions of the ratchet side and the smooth side. The retaining hook has a horizontal arm and a vertical arm installed under the horizontal arm. The horizontal arm can move horizontally across the upper side of the retaining member, and the vertical arm can thus contact each of the horizontal sides of the retaining member.
It is an advantage of the claimed invention that a focus retaining mechanism of a camera with a simple design is used for simplifying the focus retaining mechanism
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.